The root of the most commonly diagnosed brain tumor in the U.S. may be found at the dentist’s office.

While dentists use dental X-rays to look for cavities, gum diseases, and infection, they may also put a patient at risk for developing the brain tumor meningioma, according to a recent American Cancer Society study.

But local dentists said improved X-ray equipment and procedures could counter this finding.

"These individuals [from the study] had had radiographs over several years," said Axel Ruprecht, a professor and the director of oral and maxillofacial radiology at the University of Iowa College of Dentistry. "Over that time, the speed of our receptors — speed of films, or digital receptors — has increased markedly."

Ruprecht said the increased speed has resulted in decreased radiation required for radiographs.

He said more advanced equipment allows dentists to use one-sixtieth of the radiation that had been used since the beginning of dental X-ray use.

Howard Gamble, the president of the Academy of General Dentistry, said current dental technology has reduced radiation by as much as 80 percent.

Gamble said children in particular shouldn’t start doing bitewing X-rays — requiring patients to bite on a small tab for an image of the upper and lower back teeth — until age 13 when they have all their permanent teeth. Routinely, people get bitewing X-rays once a year, but patients with good oral health history can go two or three years.

Although the study relies on patients’ recall of dental X-rays, researchers said this is the largest case-control study to date, examining the correlation between meningioma and dental X-rays and the effects of exposure over time.

Patients should be aware of the amount of radiation they’re exposed to, said Jim Crall, professor and chair of public health and community dentistry at the UCLA Center for Healthier Children, Families and Communities.

Dentists, Crall said, avoid taking X-rays unless it’s necessary.

One method to curb excessive X-ray use is the caries management by risk assessment, which takes into account outside factors before an X-ray is taken.

"[Dentists] certainly know [they] should be doing a risk assessment for pediatric patients … this definitely helps all dentists minimize possible risk of radiation — [we] depend on it for good dentistry," said Colleen Greene, a third year dental student at Harvard School of Dental Medicine and president of the American Student Dental Association.

Ruprecht said dental students at the UI undergo several radiology-based courses and are trained in how to identify when radiographs are necessary.

The study, published last week, examined dental X-rays — the most common source of ionizing radiation — and the risk of intracranial meningioma, caused by ionizing radiation.

Performed by U.S. cancer specialists, the study was a population-based-case-control study including 1,433 patients who were diagnosed with meningioma, a tumor that accounts for about 27 percent of primary brain tumors. Researchers measured the association between diagnosis of the disease with reported bite-wing, full-mouth, and panorex dental X-rays and found patients who had tumors were more than twice as likely to report receiving at least one bitewing X-ray.

The American Dental Association has reviewed the study and encourages further research for patient safety, according to a press release.

Yet as oral diseases can’t be detected from visual and physical examinations alone, dental X-rays are essential to provide information on a patient’s oral health, dental experts said.

"There’s no need to worry that X-rays are going to kill you," Gamble said. "The risk now is of patients being afraid and not allowing X-rays to be [performed] is much more significant."

Editor’s Note: appended 04/19/12:

The headline on a previous version of this story said technological advances reduce the risk of cancer. Now corrected, the headline should indicate the technology reduces the risk of tumors.